Chapter Five, Exercise 5.42 Consider the following reaction: CH 3 OH(g)---> CO(g

Question

Chapter Five, Exercise 5.42

Consider the following reaction:
CH3OH(g)---> CO(g) +2H2(g)     +90.7 kJ a.) Is heat absorbed or released in the course of thisreaction? b.) Calculate the amount of heat transferred when 45.0 g ofCH3OH(g) is decomposed by this reaction at constantpressure. c.) For a given sample of CH3OH, the enthalpychange on reaction is 25.8 kJ. How many grams of hydrogen gas areproduced? What is the value of H for the reverse of theprevious reaction? d.) HOw many kilojoules of heat are released when 50.9 g ofCO(g) reacts completely with H2(g) to forCH3OH(g) at constant pressure? Chapter Five, Exercise 5.42

Consider the following reaction:
CH3OH(g)---> CO(g) +2H2(g)     +90.7 kJ a.) Is heat absorbed or released in the course of thisreaction? b.) Calculate the amount of heat transferred when 45.0 g ofCH3OH(g) is decomposed by this reaction at constantpressure. c.) For a given sample of CH3OH, the enthalpychange on reaction is 25.8 kJ. How many grams of hydrogen gas areproduced? What is the value of H for the reverse of theprevious reaction? d.) HOw many kilojoules of heat are released when 50.9 g ofCO(g) reacts completely with H2(g) to forCH3OH(g) at constant pressure?

Explanation / Answer

   (a) Since H is positive , in thisreaction heat is absorbed .    (b) 45.0g of CH3OH(g) =45.0g / moar mas of CH3OH(g)                                          = 45.0g / 32g.mol-1                                         = 1.4mol            Amount of heat transferred = 1.4mol*90.7kJ.mol-1                                                        = 127.5kJ    (c)   H for the reverse ofthe previous reaction = - H for the previousreaction                                                                            =-90.7kJ/mol                 25.8kJ = x mol *90.7kJ/mol                    x = 25.8/90.7                       = 0.2844mol                       Moles of H2 gas released= 2*0.2844mol                                                =0.5689 mol         Grams of H2 gas =0.5689mol * molar mass of H2                                  =  0.5689mol * 2g/mol                                  = 1.14g (d) 50.9 gof CO = 50.9g/ molar mass of CO                              =50.9 g / 28g.mol-1                            = 1.81mol               Heat releasesd = 1.81mol * 90.7kJ/mol                                       =164.8kJ               Heat releasesd = 1.81mol * 90.7kJ/mol                                       =164.8kJ

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